IdentittyHashMap Iterator has bug in it.
----------------------------------------
Key: DIRMINA-452
URL: https://issues.apache.org/jira/browse/DIRMINA-452
Project: MINA
Issue Type: Bug
Components: Core
Affects Versions: 1.1.2, 1.0.5, 1.1.1, 1.0.4, 1.1.0, 1.0.3, 1.0.2, 1.0.1,
1.0.0
Environment: Java, all 1.5 and 1.6 versions at least.
Reporter: Rupert Smith
Fix For: 1.1.3, 2.0.0-M1
There is a bug in IdentityHashMap Iterator which causes an infinite loop. This
can manifest itself anywhere that the iterator.remove() method is called, in
conjunction with the put() method. In particular this has been observed in the
VmPipeIdleStatus checker.
Certain sequences of puts/iterator.removes cause the map to allow put() to be
called with a full table. The code then loops round the table forever looking
for a free slot to add the new entry to.
A bug report has been submitted to Sun for this problem.
Suggested work arounds:
Use HashMap instead of IdentityHashMap.
Do not use the remove() method on the iterator, find all elements to remove in
one step, then remove in another.
Here is some sample test code that exhibits the bug in isolation. Call it
repeatedly with n=1000, until it locks up:
public void testRandomPutRemove(final int n)
{
final Map<TestElement, TestElement> idMap = new
IdentityHashMap<TestElement, TestElement>();
final Random r = new Random();
final float removeProbability = r.nextFloat();
final float addProbability = r.nextFloat();
final Queue<String> opSequence = new LinkedList<String>();
Runnable tester =
new Runnable()
{
public void run()
{
for (int i = 0; i < n; i++)
{
if (r.nextFloat() < addProbability)
{
synchronized (idMap)
{
TestElement e = new TestElement();
idMap.put(e, e);
opSequence.offer("put");
}
}
else
{
synchronized (idMap)
{
Iterator it = idMap.keySet().iterator();
for (int j = 0; it.hasNext(); j++)
{
it.next();
if (r.nextFloat() < removeProbability)
{
it.remove();
opSequence.offer("remove " + j);
}
}
}
}
}
}
};
Thread testThread = new Thread(tester);
testThread.start();
try
{
testThread.join(5000);
}
catch (InterruptedException e)
{
fail("Test interrupted.");
}
if (testThread.getState() == Thread.State.RUNNABLE)
{
System.out.println("opSequence = " + opSequence);
System.out.println("removeProbability = " + removeProbability);
System.out.println("addProbability = " + addProbability);
// Wait forever here, to give an opportunity to take thread/heap
dumps etc.
try
{
testThread.join();
}
catch (InterruptedException e)
{
// Ignore.
}
}
}
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
